"I like the games that let grown-ups and kids play together," says Come Out and Play co-founder Catherine Herdlick. "I think it's really important for kids to see adults letting loose."

The festival of public games and activities, which starts Saturday in San Francisco, harnesses that childlike impulse to turn any park or public space into a playground via safe, kid-friendly - as well as adult-friendly - games devised by artists and game designers.

Saturday's program will feature games ranging from an Alphabet Scavenger Hunt and hopscotch race that will appeal to the toddler set, to a more complex treasure hunt, the Hunt for Black Bart's Hidden Hoard, that will take players through the South of Market district in search of the famous bandit's swag. There will be a giant game of Dots and Squares - and for the more strategically minded, an enormous whiteboard will be set up for a game called Doodle Defense, in which players will draw mazes and towers designed to stop projections of enemy invaders.

Come Out and Play started in 2006 in New York City, when Herdlick and four other game designer friends piloted the festival as a way to allow families a chance to enjoy public spaces with a fresh perspective. When Herdlick moved to the Bay Area in 2009, she brought the idea with her, and the first San Francisco festival took place in 2010.

"The ethos of Come Out and Play is community, so a lot of the games are designed so that a kid could play an older person and one wouldn't have an advantage over the other," she says, noting that the games are chosen from a pool of proposals in the spring. "We choose games that sound fun to play, sound easy to explain. (We) don't want things that are complex, and we look for games that make good use of public spaces. We like games that rethink how the space is used, so a park bench is not just used for sitting, and a basketball court isn't used for basketball."

With some 35 games scheduled over the duration of the festival, which runs through Dec. 2, there is a little bit of something for everyone, from Undercover Assassins and Jericho - a kind of capture the flag - to hula-hoop tag.

"Some are quick plays and take only five minutes, and some might take half an hour," she says. "Some might take as long as four hours, but the average game is about 20 minutes long."

Organizers this year are partnering with the San Francisco Parks and Recreation Department as well as SOMArts, and Herdlick says that though all the events are free and preregistration is not mandatory, signing up online (playsf.eventbrite.com) allows you to take care of the waiver beforehand. All kids under 18 will need a parent or guardian's permission to play, and younger kids will need to have a parent with them.